Throughout this application, various publications are referenced by Arabic numerals with parentheses. Full citations for these publications may be found at the end of the specification immediately preceding the claims. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein.
Members of a protein complex called very late antigens (VLA) are expressed on the surface of T-cells (1-4). The VLA proteins constitute a family of six distinct heterodimers (VLA-1-6) that all share a common 110 kDa (non-reduced, MR) VLA subunits but differ in their .alpha. subunits which range in their molecular weights from 200 to 130 kDa (.alpha.1-.alpha.6) (5,25). Reportedly, the common .beta.-subunit of a VLA protein is involved in cell adhesion to fibronectin and laminin and VLA-5 heterodimer has been found to be identical to the human fibronectin receptor (6).
The N-terminal sequences of the VIA .alpha. subunits are homologous to the .alpha. subunits of the LFA-1, Mac-1 (CR-3) and P 150/95 molecular family, as well as to the vitronectin receptor-platelet GP IIb/IIIa family, and a position-specific (PS) antigen important in Drosophila embryogenesis (7). Many of these molecules recognize ligands containing Arg-Gly-Asp sequences and are members of the supergene integrin family of adhesive protein receptors which have been highly conserved during evolution (8,9).
In long-term cultured T cells, the major VLA protein expressed are VLA-1 (200/110 kDa) and VLA-2 (165/110 kDa) (1,2). To a lesser intent, VLA-3 (150/110 kDa) is also expressed (5). The identification of these specific members of the VLA family was facilitated by the development of monoclonal antibodies (MoAbs) that specifically recognize each heterodimer (4,5,10).
A new monoclonal antibody (MoAb), 1B3.1, which reacts with a novel VLA-1 epitope is described herein. Since 1B3.1 was raised against T cells belonging to the T.gamma. lineage, our data surprisingly show that T cells of this lineage may also express receptors for cell matrix adhesion-related proteins, which may be of importance in the various functions of this subset of T cells.
Neils Odum, et al. (29) has described the increased prevalence of last stage T cell activation antigen or VLA-1 in active juvenile chronic arthritis. The increased prevalence was measured using a panel of MoAbs including a monoclonal antibody, anti-VLA-1 MoAb, TS2/7 (Coulter clone)(1) which specifically recognizes a molecular determinant, i.e. epitope, on the VLA-1 molecule or the VLA-1 protein. MoAb TS2/7 recognizes a VLA-1 epitope distinct and separate from a VLA-1 epitope recognized by MoAb 1B3.1. An experiment was performed which accessed the ability of MoAbs 1B3.1 and TS2/7 to block the binding TS2/7 to VLA-1. 1B3.1 MoAb was unable to inhibit the binding of .sup.125 I-TS2/7 in this assay (FIG. 5). In contrast, unlabeled did inhibit the binding of the iodinated TS2/7. This result confirmed that MoAb TS2/7, but not IB3.1, was able to block FITC/conjugated TS2/7 stain of activated T cells. Accordingly, 1B3.1 and TS2/7 recognized non-overlapping epitopes of the VLA-1 molecule.
The subject antibody provides the following advantages: a) a means to identify a previously unidentified epitope of the VLA-1 molecule, b) a means to identify a subset of T cells expressing VLA-1, c) a means to identify a subset of T cells associated with certain inflammation-related diseases and d) a means to elucidate in detail the structure and functions of the VLA-1 molecule in conjugation with other monoclonal antibodies which recognize an epitope on VLA-1.